ROS Test

This is a simple programming assignment designed to test your abilities to use ROS to solve a problem.

Background

LeoRover

At Discover, we use LeoRovers as our UGVs. Information about the LeoRover can be found here. The LeoRovers use a series of ROS topics and nodes to control and access different components and sensors. The full rqt graph of the topics and nodes is below.

Important Topics

The most important topics for the operation and sensing of the LeoRovers include:

• /cmd_vel: This topic is used to move the rover by turning the wheels. The topic listens for geometry_msgs/Twist messages.
• /wheel_odom_with_covariance: This topic contains a lot of useful information about the current position and velocity of the robot. Information is published in the format of a nav_msgs/Odometry message.
• /joint_states: This topic also contains a lot of useful information about the current position and velocity of the robot. Information is published in the format of a sensor_msgs/JointState message.
• /imu/data_raw: This topic contains useful information published from the robot's inertial measuring unit. Messages on this topic are published in the sensor_msgs/Imu format.
• /camera/image_raw: This topic is used by the raspicam to publish image data. Images are published in the sensor_msgs/Image format.

ARTags

ARTags are markers that are used to support 3D alignment and tracking in augmented reality systems. More information about ARTags can be found here. We use the ar_track_alvar ROS package to generate and track ARTags. Launch and configuration files used to integrate this package with the LeoRovers are included in our RoverAPI package.

The Task

Your task is to create a ROS package that utilizes the topics published by the LeoRover and the ar_track_alavar package to have the robot follow an ARTag as it moves. The video below shows the desired behavior from the robot in the rear it follows the ARTag on the robot in the front.

Notes

• The rover should maintain a following distance of about half a meter. It does not need to be exactly half a meter behind the ARTag at all times, but it should be close.
• The rover should be able to follow the ARTag in multiple directions. If the ARTag veers to the left or right, the rover should turn accordingly. If the ARTag backs up, so should the rover.

ARTag.mp4

Tools

We have created a docker container image that has the capability of simulating both LeoRovers and ARTags for you to test your ideas. Information about the container image and usage can be found here.

Submission

Please fork this repository and keep all of your work within the forked repository. When you are ready to submit, email us a GitHub link to the forked repository. Please write all of your code in the form of a ROS package. Your submitted repository should make use of the common files/structure used by ROS packages (i.e. package.xml, CMakeLists.txt, /scripts, /src, etc). Please overwrite this README.md file with your own. Your README.md file should contain instructions on how to run your code (i.e. launch files to use, Python scripts and/or ROS nodes to run, etc).